Blue-flame gun burner process and apparatus for liquid hydrocarbon fuel



Dec. 8., 1970 F. W. BAILEY BLUE-FLAME GUN BURNER PROCESS AND APPARATUS FOR LIQUID HYDROCARBON FUEL Filed Sept. 23, 1968 14 r 1g 35 r 54 Frank M 2 Sheets-Sheet 1 INVENTOR. 50 26y Dec. 8, 1970 Filed Sept. 23,

BLUE-FLAME GUN BbRNER PROCESS AND APPARATUS F w. BIAILEY 3,545,902

FOR LIQUID HYDROCARBON FUEL 2 Sheets-Sheet 2 125 S 56 7125' 126' FUEL. 5 21 34 I'M/f E 3g 10 65 I flccfssoRy 1W PACK/7G5 INVENIOR. 9 917 Fran/f W Badey fl? ORNEYS' United States Patent Int. Cl. F23m 9/00 US. Cl. 431--9 20 Claims ABSTRACT OF THE DISCLOSURE Blue-flame gun burner process and apparatus for burning liquid hydrocarbon fuel, such as fuel oil to produce a stable blue flame which is quiet and sootless for air pollution reduction purposes and has numerous other advantages. A compact inexpensive burner unit is described adapted to be used in new home furnace installations and to be used as a replacement unit capable of being inserted into existing furnace fireboxes to replace conventional gun-type yellow flame burners. Also a blue-flame water heater system is disclosed suitable for providing convenience hot Water or for use as a home heating furnace, which recovers the heat of vaporization of the Water vapor (H O gas) which is present in the gaseous combustion products resulting from burning fuel oil, thus increasing thermal efficiency substantially above that obtained for conventional Water heaters or furnaces. Moreover, the invention provides a multi-fuel blue flame burner unit which is capable of burning fuel oil, kerosene or gasoline interchangeably While providing substantially the same blue flame characteristics thereby being convenient for mobile home applications, etc.

The present invention relates to blue-flame gun burner process and apparatus for burning liquid hydrocarbon fuel to produce a stable blue flame which is quiet and provides more complete combustion, eliminating particulate matter in the exhausted products, thereby contributing to substantially reduced air pollution and providing numerous operating advantages, as will be explained further below.

Conventional gun-type burners which have been in use prior to the present invention produce yellow or yellow ish orange flames which are noisy, are characterized by incomplete combustion, and often deposit soot in the flue or chimney or discharge particulate matter into the atmosphere. Also, any cool areas within the firebox tend to quench the yellow flame, stopping further combustion in localized regions and leading to the precipitation of unburned carbon on the cooler areas of the heat exchangesurfaces of the firebox. These carbon deposits impede heat transfer and reduce efliciency.

Among the advantages of the blue-flame burner process and apparatus of the present invention are those resulting from the fact that they enable liquid hydrocarbon fuel, such as fuel oil, to be burned with a quiet, stable blue flame in which substantially complete combustion occurs. The firebox and heat exchange surfaces remain cleaner than with conventional yellow-flame gun burners, improved heat transfer occurs, and reduced maintenance and down time are achieved. The blue flame produced by utilizing this invention to burn fuel oil has characteristics similar to those which are present in conventional gas burners. Accordingly, this invention opens up the 3,545,902 Patented Dec. 8, 1970 possibility of utilizing fuel oil in various installations which have heretofore been limited to gas burners.

The invention provides a compact, inexpensive burner unit adapted to be used in a wide variety of new installations as well as being adapted for use as an improvement replacement unit for existing yellow flame gun burner installations. The gun barrel of the burner can be conveniently inserted through a port into a firebox in a manner to replace a conventoinal gun-type yellow flame burner.

Among further advantages arising from certain aspects of the present invention are that they provide a blueflame water heater system wherein the gaseous products of combustion are confined in a forced draft flow in close association with heat exchange surfaces coupled with the water tank. The heat is extracted thoroughly from the gaseous products of combustion with the result that the water vapor is condensed on the heat exchange surfaces, thus extracting the heat of vaporization rather than condensing moisture in the flue or chimney as occurs in conventional water heater systems. Thus, a higher thermal efliciency is obtained than with conventional water heater installations. In addition, the condensing moisture serves to trap and remove sulphur compounds from the gaseous combustion products before they are discharged into the atmosphere, substantially eliminating undesirable pollutant products.

A summary of the features and advantages of the blueflame gun burner process and apparatus embodying the present invention includes the following list:

1) A compact, light weight burner unit is provided, which is self-cooling in operation.

(2) The process and apparatus are versatile for use in many different applications and environments including many of those which have heretofore been limited to gas burners.

(3) A clean blue flame is produced, contributing to substantially reduced air pollution.

(4) The noise level of the blue flame is lower than that for yellow flame combustion. Moreover, the burner starts Without a loud pressure pulse or bang because there is no substantial pressure build-up during transient starting conditions.

(5) The process and apparatus are reliable in operation.

(6) The burner unit is easy to service. It is so compact and light Weight that it can quickly and conveniently be replaced by another burner unit so that the original can be returned to the maintenance plant, thus providing centralized servicing using interchangeable, compact burner units.

(7) The apparatus and systems shown are simple, reliable and low in cost.

(8) A multi-fuel burning capability is provided by the process and apparatus. Fuel oil, kerosene or gasoline may be used while providing substantially the same blue flame characteristics, thereby being convenient for mobile home applications, garages, remote locations where fuel availability is limited, etc.

(9) The many novel aspects of the invention enable fuel oil and other liquid fuels to be utilized more efficiently and more conveniently.

The various aspects, objects and advantages of the present invention will in part be pointed out and will in part become apparent from the following description when considered in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of compact, portable, lightweight inexpensive gun burner apparatus embodying and for practising the process of the present invention;

FIG. 2 is a top plan view of the burner apparatus of FIG. 1, shown on enlarged scale with portions of the cover and barrel removed to reveal interior parts;

FIG. 3 is a side elevational sectional view taken along the line 33 of FIG. 2;

FIG. 4 is an enlarged cross sectional view of the barrel portion of the apparatus, taken along the plane 44 in FIG. 2;

FIG. 5 is a side elevational sectional view illustrating the blue flame gun burner process, the gun barrel being inserted through a conventional-size port into the firebox of a domestic furnace; and

FIG. 6 is an elevational sectional view of an efficient compact water heater system of high volumetric heat transfer capacity embodying the present invention.

Referring to the drawings in greater detail, the blue flame gun burner process and apparatus as illustrated in FIGS. 1 through 5, produce a quiet, stable blue flame when burning liquid hydrocarbon fuels and are well suited for burning fuel oil, kerosene or gasoline, interchangeably; and in the following description the particular fuel being burned is No. 2 fuel oil. The burner apparatus includes a gun-shaped barrel 10 extending from a housing 12, the barrel and housing together constituting a compact, light-weight burner unit which is readily portable. The barrel 10 extends from the front wall 14 of the housing, and a curved top cover 16 is hinged by a piano type hinge extending along a line at 17. Thus, the curved cover 16 can be unlatched by latches 15 and can be swung up to open the entire interior of the housing 12, as indicated in FIG. 3 at 15' and 16 by dashed and dotted lines, for convenient in inspection and servicing the burner unit. A handle 18 attached to the cover 16 may be used for carrying the entire burner unit by one hand.

In operation the interior of the housing 12 becomes pressurized by a centrifugal blower fan 18, (FIGS. 2 and 3) for reasons to be explained in detail further below. In this illustrative embodiment the blower fan 18 is located immediately adjacent to an end wall 20. An air intake port 22 in the end wall 20 containing a filter 23 is aligned with this blower fan, and both the primary air and the secondary air are drawn through the intake port 22 so that the filter 23 serves to filter both primary and secondary air.

Within the housing 12 are located the following components: the blower fan 18, discussed above, an electric motor 24, a primary air compressor 26 and an ignition transformer 28. The motor 24 drives the fan 18 and drives the air compressor 26. This air compressor 26 is illustrated as being a positive-displacement compressor of the vane-type containing an internal air filter for providing further filtering of the compressed primary air, which is utilized to atomize the liquid fuel as will be explained.

From the compressor 26 the compressed air passes through a hose line 29 (FIGS. 2 and 3) to an air relief vlave 30, which is a conventional spring-loaded pressure relief valve having an adjusting screw, as seen in FIGS. 2 and 3, for adjusting the pressure level at which this valve will open. In order not to labor the air compressor 26, the relief valve 30 is set to a level as low as practicable with a given liquid hydrocarbon fuel, generally pressure level is slightly increased when dealing with more viscous fuel, being usually set in a range of 3 to 7 psi. above atmospheric pressure. From the relief valve 30 a hose line 31 (FIGS. 2 and 3) carries the primary air to an air atomizing nozzle for liquid fuel such as fuel oil, the liquid fuel being supplied through a fuel line 34 (FIGS. 1 and 3) from a suitable source of fuel such as a fuel tank. The fuel may be pumped or gravity fed to the fuel line 34, which is connected through a tube 35 and a short coupling hose 36 extending to the nozzle 32.

As shown in FIG. 5 the fuel nozzle 32 produces a cone shaped spray pattern 38 of finely divided droplets of fuel mixed with a high velocity flow of the primary air. In order to ignite the fuel spray a spark plug is arranged to produce an ignition spark at the location X in FIG. 5. This spark plug is shown at 40 in FIGS. 2 and 3, but it is omitted from FIG. 5 in order to simplify the drawing for purposes of explaining the blue flame combustion process.

The ignition transformer 28 provides a suitable high voltage, such as 10,000 volts, which is supplied from an insulated high voltage terminal 42 through an insulated high voltage wire 43 connected to the center electrode of the spark plug 40.

The electrical energy for the motor 24 and for the ignition transformer 28 is supplied through an electrical cord 44. Thus, it is seen that the gun burner unit provided by this invention is well adapted for replacement servicing, for there are only two lines to be disconnected, nameIy, the fuel line 34 and the electrical power line 44. Each of these lines includes a quick disconnect coupling (not shown) to facilitate removal of the burner unit from an installation. In this way it can be quickly replaced with an identical substitute unit, while the original unit is returned to the servicing plant for overhaul.

The front wall 14 includes an outer metal panel covered on its interior with a layer of thermal insulation 46, such as fibrous glass or asbestos. The curved top cover 16, end wall 20, the opposite end wall, and the base 48 are each formed by sheet metal lined with a layer of sound absorbent material 49, such as fibrous glass batting, which also provides thermal insulation. Thus, the unit is vrey quite in operation for any noise which may be generated by the fan 18, motor 24, or compressor 26,

is confined and absorbed within the housing 12.

Moreover, the components within the housing are all effectively cooled during operation by virtue of the fact that they are surrounded by insulation 46, 49, while fresh air is continuously being drawn into the housing through the intake port 22 serving to cool the entire interior of the housing 12.

The burner unit can conveniently be mounted in either of two waysby standing on its feet 50 or by attaching the front wall 14 to the side of the furnace, as by a pair of hooks and eyes (not shown).

A typical installation for the burner unit is shown in FIG. 5 in which the barrel 10 is inserted through an opening 52 in the wall 54 of a domestic space heating furnace having a fire box 56. It is noted that the over-all diameter of the barrel 10 is only 4.0 inches, which corresponds with the size of the vast majority of conventional yellow flame gun burners in use today for home heating purposes. Therefore, the burner unit as shown is adapted for improving existing furnace installations by replacing yellow flame gun burners as well as for new furnace installations and other installations.

The gun barrel 10 includes an inner cylindrical metal sleeve element which serves to define a mixture preparation chamber or zone 62 having axial flow therein, as will be explained in detail. Also, the cylindrical wall means 60 serves to separate the zone 62, wherein mixture preparation chemical processes are occurring, from an annular recirculation path region 64. In this path region 64 surrounding the wall means 60' there are recirculating gases 67 which are being returned for purposes of mixing with and diluting the fresh incoming mixture 38. As shown in FIG. 4, the annular region 64 is sub-divided into a plurality of paths 65 in parallel flow relationship by means of a separator 66 of metal of good heat conduction characteristics. This separator 66 is shown in FIG. 4 as having a star shape, thus providing a plurality of radially extending metal webs in heat conducting relationship with the sleeve element 60 and in heat transfer relationship with the gases 67 recirculating through the multiple paths 65. Thus, the recirculating gases '67 are cooled down substantially to moderate temperature as they pass through the multiple passages 65. These recirculated gases include products of combustion and may include vaporized fuel.

The inner cylindrical Wall means 60 is shown as having a diameter of 2.0 inches. It is surrounded by second wall means 68, shown as an intermediate cylindrical element 68, having a diameter of 3.0 inches and which is formed of metal of good heat conduction characteristics. The second wall means 68 engages the periphery of the separator 66 in good heat exchange relationship therewith. Continuing forward beyond the forward end 70 or mouth of the inner cylindrical wall means 60, the second wall means 68 progressively enlarges by expanding along an outwardly flaring conical wall 72 which expands out to define a gaseous fixation flow region 74 of substantially augmented cross sectional area. In this embodiment the maximum diameter of the expanded wall portion 76 surrounding the gaseous fixation region 74 is a full 4.0 inches. Thus, the gaseous fixation region 74 of augmented flow area has a cross sectional area four times larger than the mixture preparation zone 62. An annular baffle 78 extends inwardly from the maximum diameter wall portion 76 toward the gaseous fixation region 74, and beyond this baflie 78 there is a converging wall portion 80 having numerous perforations 81. This converging Wall portion 80 defines the muzzle of the burner from which a blue flame 82 is projected during operation.

Attention is invited to the fact that the expanding wall section 72, the maximum diameter wal part 76, and the converging wall portion 80 collectively define a streamlined shell generally indicated at S of generally ogival shape. This streamlined ogival shell S is a flame-holding member and its shape avoids the generation of acoustical disturbances and contributes to quiet blue flame combustion.

Secured to the front housing wall 14 is the outer cylindrical element 84 of the barrel 10. This outer barrel element 84 has a diameter of 4.0 inches, and it extends forward to terminate closely adjacent to the expanding wall 72, thus defining an annular discharge throat 85 near the back of the streamlined shell S. As shown in FIG. 4, the intermediate sleeve 68 is supported within the outer barrel element 84 by means of a plurality of radially extending fins 86.

In order to provide a large flow of tertiary air, an annular passage 88 between the outer barrel element 84 and the second Wall means 68 communicates with the pressurized interior of the housing 12. There is a substantial pressure differential existing between the pressurized interior of the housing 12 and the annular dis charge throat 85. The resulting large flow of tertiary air through the annular passage 88 is indicated by the arrows 90.

Surrounding the nozzle 32 is a baffle 92 which is connected at its periphery to the back end of the intermediate cylindrical element 68. The periphery of the batfle 92 is sloped forwardly at 93 to accommodate streamlined flow 90 of the tertiary air into the passage 88. Also, the sloping surface 93 aids in directing the recirculated gases 67 inwardly into the mixture preparation zone 62. Surrounding the entrance to the mixture preparation zone 62 is a converging throat section or baflle means 94 which aids in directing the recirculated gases into intimate mixing with the fresh fuel and air mixture 38. The converging baffle means 94 also serves to create localized eddying action which contributes to reliable ignition. If the localized eddy creating means 94 are removed from the entrance to the mixture preparation zone 62, I have observed that reliable ignition does not occur. In addition the eddy creating means 94 tends to deflect fuel droplets away from the inner surface of the wall means 60, thus preventing a build-up of a film of unburned fuel thereon, and l have observed that the prevention contributes to reliable ignition.

In the bafile 92 there are a few small apertures 96 which admit a flow of secondary air into the region near the entrance to the mixture preparation zone 62. This admission of air through the apertures 96 provides for secondary oxygen flow into the Zone 62 which causes preoxygenation of the fuel in the zone 62.

Before discussing the blue flame gun burner process in detail it will be helpful to note the relative cross sectional areas of (1) the mixture preparation chamber in the axial flow region 62, (2) the annular recirculation path 64 comprising multiple passages 65, and (3) the annular flow passage 88. These are as follows:

Cross section area in square Cross sectional area of- Function ofinches (DZ-Df 5 4..

(1) Chamber 62 (2) Annular recirculation path 64 (3) Annular path 88 Blue flame gun burner combustion process In the blue flame gun burner combustion process the fresh mixture 38 of atomized liquid fuel and primary air is injected through the converging throat 94 into the back end of the mixture preparation zone 62. This spray pattern of fresh mixture 38 is travelling forward at high velocity as it approaches and passes through the throat section 94, thus creating a low pressure L in the region near the back end of the zone 62. Recirculated gases 67, which include combustion products and also include vaporized unburned fuel, thus being a fuel-vapor rich mixture of combustion products having no significant oxygen content, are drawn back into the low pressure region L so that they will become thoroughly intermixed with and thus dilute the fresh fuel-air mixture 38.

In the mixture preparation zone 62 the fuel-air mixture 38 is thoroughly intermixed with and is diluted by a large proportion of recirculated gases 67. The amount of recirculated gases in at least 40 molal percent of the fresh incoming fuel-air mixture 38 being diluted thereby. That is, if the fresh fuel-air mixture entering the zone 62 is 100 molal units, then the recirculated and cooled diluent gases 67 is at least 40 molal units, so that the ratio is at least 40 molal percent, as stated.

There is substantially no visible combustion occurring within the mixture preparation zone 62, except during the momentary transient occurring at start-up when ignition occurs at the point X. In other words, combustion is suppressed within the mixture preparation zone 62 by the large proportion of recirculated gas which created a chemically reducing atmosphere within this zone. i.e., a fuel rich mixture therein.

The substantial cooling of the recirculated gases 67 which occurs in the multiple paths 67 also contributes to the suppression of combustion in the mixture preparation zone 62. The secondary air 96 passing through the apertures in the bafile 92 serves to pre-oxygenate the diluted mixture 38 which aids in producing blue flame combustion further downstream.

Thus, a cooperative action of (l) cooling the recirculating gases 67 to set up favorable kinetics and of (2) diluting the fresh mixture with this cooled diluent and (3) controlling the oxygen fraction of the composition in zone 62 and in the region 74 provide operation in the blue flame regime.

An advantage of this reducing atmosphere which exists in the annular recirculation path 64 and in the zone 62 is that it prevents oxidation and provides an effective steam-cleaning action. The combustion products, being the result of burning a liquid hydrocarbon fuel contain water vapor as one of the major constituents. This water vapor produces a steam-cleaning action of the elements 60, 66, 68, 92, 93, 94, 72, 76, 32 and so that they remain clean in operation, thus reducing maintenance and extending operating life and efficiency.

Visible combustion begins beyond the mouth as the diluted fuel-air mixture expands into the gaseous fixation region 74. By virtue of the expanded cross sectional flow area in fixation region 74, the velocity of the gases slows down, and hence their pressure rises so as to create a higher pressure H in this region 74. This higher pressure H propels a large proportion of the products of combustion back along the recirculation path 64 toward the low pressure region L, as indicated by the flow arrows 67. The annular baffle 78 serves two functions. It creates an annular stagnation zone wherein the localized pressure is increased as indicated at H, thus producing a large recirculation flow 67. Also, it prevents mixture of oxygen with the recirculated gas products. That is, the baflle 78 prevents any tertiary air 90 which enters the perforations 81 from flowing back into the recirculating gases 67. If the bafile 78 is removed then a sudden external draft or wind can cause the tertiary air 90 to begin mixing with the recirculating gases 67, and then suddenly the quiet blue flame 82 can abruptly turn into a roaring yellow fiame. The baflle 78 prevents such an undesired transition.

During normal blue flame operation, the hottest part of the barrel tends to be the lip of the mouth 70. To draw away the heat, the first wall means 60 is formed of thicker gage metal.

The tertiary air flow 90 cools the intermediate cylindrical element 68 and thus cools the separator 66 and hence cools wall means 60. The tertiary air 90 issues through the annular discharge throat 85 at high velocity and washes over the generally egg-shaped streamlined shell S in clinging relationship with its convex exterior surface, as indicated in FIG. 5 by the arows 90. Thus the shell S is effectively cooled.

A portion of the tertiary air passes inwardly through the perforations 81 to participate in supporting blue flame combustion, while the remainder of the tertiary air joins into the blue flame 82 beyond the muzzle of the barrel 10 to complete combustion of the fuel in a clean blue flame. The converging configuration of the wall portion 80 accelerates the flame forwardly, thus increasing its velocity and causing a reduction in pressure which aids in drawing tertiary air 90 inwardly through the multiple perforations 81.

The converging wall portion 80 can be omitted to obtain certain operating characteristics which are advantageous for use in larger fireboxes 56 where a greater heat output is desired. Omission of the converging section 80 opens up the muzzle of the barrel 10, which provides a blue flame 82 that spreads out in a bushey configuration, i.e. a generally more spherical configuration, adapted for a larger firebox. Also, the amount of fuel burned per hour can be increased when the muzzle is thus opened.

Compact eflicient blue flame water heating process and apparatus In FIG. 6 is illustrated a compact efficient blue flame water heating process and apparatus. The gun barrel 10 is separate from the housing 12A which constitutes an accessory package. Package 12A contains the same components as the housing 12, except that the blower fan 18 is omitted. There is a forced draft suction blower 114 which causes a vigorous flow of tertiary air 90. As shown in FIG. 6 the gun barrel 10 is aimed vertically upwardly, and the outer cylindrical wall means 84 are in the form of a vertical duct having a bell mouth for directing 8 flow of tertiary air 90 therein. This tertiary air flow duct 84 is connected into a bottom chamber 102 of a water heater 104, so that this bottom chamber 102 provides a fire box commumnicating with a central heat exchange conduit 106, which is surrounded by an annular water tank 108.

Surrounding the tank 108 is an annular heat exchange passage 110 through which the products of combustion are drawn downwardly into a discharge line 112 by means of the suction blower 114 connected to a flue 116. A top heat exchange chamber 118 extends radially out to provide communication between the central conduit 106 and the annular passage 110. A layer of thermal insulation 120 surrounds the annular passage 110 and overlies the top chamber 118. Extending down in the annular passage 110 are multiple heat exchange fins 122. The water heater 104 is supported on legs 128 which provide for access and allow admittance of the tertiary air flow 90. It is noted that this tertiary air flow is a high velocity flow, being drawn by the suction blower 114.

Water to be heated enters the tank 108 through a pipe line 124 and hot water is supplied through a line 126. This hot water may be used for convenience purposes or may be used as a heat distribution medium for supplying heat for space heating such as in a home, factory, garage or similar building.

This process and apparatus enables extraction of the higher heating value of fuel oil by recovering the heat of evaporation of the water condensible fraction of the combustion products. This raises the recovery another ten to eleven percent of available heat energy thermodynamically. :In most instances prior to this invention this heat of vaporization has been dissipated up the exhaust flue.

The fins 122 are made of non-corrodible material such as stainless steel, because the water droplets 128 condense out thereon. The water is led off through a drain tube 130 leading to a sump 132. These water droplets 128 also serve to remove any sulphur oxides which may be present, thus removing such pollutants from the atmosphere.

From the foregoing it will be understood that the illustrative embodiments of the blue-flame burner process and apparatus of the present invention for burning liquid hydrocarbon fuel are well suited to provide the advantages set forth, and since many possible embodiments may be made of the various features of this invention and as the process and apparatus herein described may be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense and that in certain instances, some of the features of the invention may be used without a corresponding use of other features, all without departing from the scope of the invention as defined by the following claims.

What is claimed is:

1. A blue-flame gun burner process for burning liquid hydrocarbon fuel with a blue flame comprising the steps of providing a gaseous fixation region of expanding cross section, providing a quantity of air flow around such fixation region for cooling the exterior of said region and for supporting combustion downstream from said fixation region, creating a stagnation zone in said fixation region of higher pressure, recirculating gases from said stagnation zone, cooling said recirculated gases, injecting a fresh mixture of finely divided fuel droplets and air into a mixture preparation zone upstream from said expanding fixation region, introducing said cooled recirculated gases into said mixture preparation zone, thoroughly intermixing said cooled recirculated gases with said fresh mixture for diluting said fresh mixture, introducing secondary air into said mixture preparation zone to preoxygenate the diluted mixture, expanding the resulting diluted mixture by downstream flow into said fixation region, projecting a blue flame downstream from said fixation region, and mixing said air flow with said blue flame for supporting combustion therein.

2. A blue-flame gun burner process for burning liquid hydrocarbon fuel with a blue flame comprising the steps of providing a mixture preparation zone extending along an axial flow path and a gaseous fixation region downstream from said zone, introducing finely divided hydrocarbon fuel droplets and air into said mixture preparation' zone, recirculating gases from said fixation region through an annular path surrounding said mixture preparation zone in counter flow relationship with respect to the mixture preparation zone, flowing ambient air around said annular recirculating path to cool the recirculating gases therein, introducing said cooled recirculating gases into said mixture preparation zone to be mixed with said fuel, and discharging a blue flame from said fixation zone.

3. A blue-flame process for burning liquid hydrocarbon fuel with a blue flame comprising the steps of defining a mixture preparation zone adapted to have gaseous flow passing therethrough in a predetermined direction, defining a gaseous fixation region downstream from said zone, supplying finely divided liquid hydrocarbon droplets and air to said zone moving generally in said predetermined direction, passing the flow from said zone into said fixation region, recirculating a portion of the gases from said fixation region to said zone, cooling the recirculating gases by forced air flow, mixing the cooled recirculated gases with the finely divided droplets and air in said zone, issuing a blue flame from said fixation region, passing said blue flame into an enclosed flow path, creating a suction in said enclosed flow path downstream from said blue flame, drawing the gaseous prodnets of combustion from said blue flame downstream towards said suction, and directing said forced air flow into siad enclosed flow path.

4. A blue-flame process for burning liquid hydrocarbon fuel with a blue flame comprising the steps of defining a mixture preparation zone adapted to have gaseous flow passing therethrough in a predetermined direction, defining a gaseous fixation region downstream from said zone, supplying finely divided liquid hydrocarbon droplets and air to said zone moving generally in said predetermined direction, passing the flow from said zone into said fixation region, recirculating a portion of the gases from said fixation region to said zone, cooling the recirculating gases, creating a localized eddying action at the entrance to the mixture preparation zone for mixing the cooled recirculated gases with the finely divided droplets and air in said zone, and issuing a blue flame from said fixation region.

5. A blue-flame process for burning liquid hydrocarbon fuel with a blue flame comprising the steps of defining a mixture preparation zone adapted to have gaseous flow passing therethrough in a predetermined direction, defining a gaseous fixation region downstream from said zone, supplying finely divided liquid hydrocarbon droplets and air to said zone moving generally in said predetermined direction, passing the flow from said zone into said fixation region, recirculating a portion of the gases from said fixation region to said zone, cooling the recirculated gases to set up blue flame kinetics, diluting the supply mixture of finely divided droplets and air with the cooled recirculating gases, controlling the oxygen fraction of the composition in the mixture preparation zone and in the gaseous fixation region, and issuing a blue flame from said fixation region.

6. A blue-flame gun burner process for burning liquid hydrocarbon fuel with a blue flame as claimed in claim including the step of converging the flow of the blue flame as it is projected downstream from said fixation region, and mixing a portion of said air flow with the converging flow of the blue flame.

7. A blue-flame gun burner process for burning liquid hydrocarbon fuel with a blue flame as claimed in claim 5 including the step of maintaining reducing atmospheric conditions in said recirculating gases.

8. A blue-flame gun burner process for burning liquid hydrocarbon fuel with a blue flame as claimed in claim 2 including the step of flowing said ambient air toward said blue flame.

9. A blue-flame process for burning liquid hydrocarbon fuel with a blue flame as claimed in claim 3 wherein a quantity of water to be heated is placed in heat exchange relationship with said enclosed flow path, and condensing the water vapor fraction of the products of combustion in said enclosed flow path in heat exchange relationship with said water for utilizing the heat from the condensing thereof to aid in heating said water.

10. A blue-flame process for burning liquid hydrocarbon fuel with a blue flame as claimed in claim 9 wherein condensing said water vapor fraction of the products of combustion removes sulphur oxides from said products of combustion, thereby to reduce air pollution.

11. Blue-flame gun burner apparatus for burning liquid hydrocarbon fuel with a blue flame comprising first wall means defining a mixture preparation zone, said zone having an open mouth at its front end and being open at its back end, second wall means defining an annular recirculation path around said preparation zone, said second wall means extending forward beyond the mouth of said wall means and extending in an outwardly expanding wall section reaching a diameter substantially larger than the mouth of said first wall means, said expanding wall section being connected to a converging wall section defining an enlarged hollow shell of streamlined shape having an open muzzle, separator means extending between said first and second wall means providing a plurality of heat exchange surfaces in said annular recirculation path, 'bafile means closing the back end of said second wall means, nozzle means for supplying atomized fuel and air through said baflle means along a path toward the back end of said mixture preparation zone, means for igniting the fuel, the enlarged region within said hollow shell communicating through said annular circulation path with the space between said baffle means and the back end of said mixture preparation zone for carrying recirculating gases from said region within said hollow shell to said space, and means for conducting a substantial flow of air along the exterior surface of said second wall means in clinging flow relationship around said streamlined hollow shell for supporting a blue-flame combustion being discharged from the muzzle end of said hollow shell.

12. Blue-flame gun burner apparatus for burning liquid hydrocarbon fuel with a blue flame as claimed in claim 11 in which said converging wall section has a plurality of openings therein admitting a portion of said air flow into the muzzle end of said hollow shell.

13. Blue-flame gun burner apparatus for burning liquid hydrocarbon fuel with a blue flame as claimed in claim 11 in which said baflle means has openings therein for admitting air therethrough.

14. Blue-flame gun burner apparatus for burning liquid hydrocarbon fuel with a blue flame comprising first wall means defining a mixture preparation zone, said zone having an open mouth at its front end and being open at its back end, second wall means defining a recirculation path around said preparation zone, said second wall means extending forward beyond the mouth of said wall means and extending in an outwardly expanding wall section defining an enlarged hollow shell, a plurality of heat exchange surfaces in said recirculation path, means for supplying air and for supplying finely divided fuel droplets into the back end of said mixture preparation zone, means for igniting the fuel, the expanded region within said hollow shell communicating through said circulation path with the back end of said mixture preparation zone for carrying recirculating gases from said region within said hollow shell to said zone, and means for conducting a substantial flow of air along the exterior surface of said second wall means in clinging fiow relationship around said hollow shell for supporting a blue-flame combustion being discharged from the muzzle end of said hollow shell.

15. Blue-flame gun burner apparatus as claimed in claim 14 including an annular water heater having a water tank with a central heat exchange path extending upwardly therethrough, said heat exchange path extending over the top of said tank and downwardly around the outside of said tank, a plurality of heat exchange surfaces in said path around said tank, means for draining condensed water vapor from said surfaces, and suction blower means communicating with said heat exchange path downstream from said water tank.

16. Blue-fiame gun burner apparatus as claimed in claim 14 including a housing, blower means pressurizing the interior of said housing, third wall means defining an air flow path along the exterior of said second wall means, said pressurized interior communicating with said air flow path for providing air thereto.

17. Blue-flame gun burner apparatus as claimed in claim 16 in which said third wall means defines an air discharge throat near said hollow shell for directing air flow against the exterior of said hollow shell.

18. A compact, portable blue-flame gun burner for burning liquid hydrocarbon fuel with a blue flame comprising a housing, fan means in said housing for supplying air, a barrel extending from said housing, said barrel including first wall means defining a mixture preparation zone, said zone having an open mouth at its front end and being open at its back end, second wall means defining a recirculation path around said preparation zone, said second wall means extending forward beyond the mouth of said wall means and extending in an outwardly expanding wall section defining an enlarged hollow shell, a plurality of heat exchange surfaces in said recirculation path, means supplying air and supplying finely divided fuel droplets into the back end of said mixture preparation zone, means for igniting the fuel, the expanded region within said hollow shell communicating through said circulation path with the back end of said mixture preparation zone for carrying recirculating gases from said region within said hollow shell to said zone, and third wall means for conducting a substantial flow of air supplied by said fan means along the exterior surface of said second wall 12 means in clinging flow relationship around said hollow shell for supporting a blue-flame combustion being discharged from the muzzle end of said hollow shell.

19. A compact, portable blue-flame gun burner for burning liquid hydrocarbon fuel with a blue flame as claimed in claim 18 in which said housing is thermally insulated, said fan means pressurizing the interior of said housing, the interior of said housing communicating with said third wall means for supplying said air flow, said housing containing transformer means connected to said igniting means, air compressor means connected to said means for supplying finely divided fuel droplets for atomizing the fuel, and motor means for driving said fan means and said air compressor means.

20. Blue-flame heater apparatus for burning liquid hydrocarbon fuel with a blue flame in a heater comprising first wall means defining a mixture preparation zone, said zone having an open mouth at its front end and being open at its back end, second wall means defining a recirculation path around said preparation zone, said second walls means extending forward beyond the mouth of said first wall means defining an expansion region beyond said mouth and having a muzzle, means for supplying air and for supplying finely divided fuel droplets into the back end of said mixture preparation zone, means for igniting the fuel, said expansion region communicating through said circulation path with the back end of said mixture preparation zone for carrying recirculating gases from said expansion region to said zone, means for conducting a substantial flow of air along the exterior surface of said second wall means for completing a blue-flame combustion near said muzzle, a heater in heat exchange relationship with said muzzle, a discharge line downstream from said heater, and suction means communicating with said discharge line, said suction means drawing said flow of air along the exterior of said second wall means.

References Cited UNITED STATES PATENTS 2,048,321 7/1936 Carruthers et al. 43l1l5 Re. 24,682 8/1959 Johnson 4l3-1l6 3,269,448 8/1966 Martin 43l116X EDWARD G. FAVORS, Primary Examiner US. Cl. X.R. 43 ll l6 

